When creating materials, ALICE allows users to define a material resource as either consumable or reusable. Common sense dictates the definition for each:
- Consumable resources are no longer available for the remainder of the project once they are consumed (e.g., concrete, single-use formwork, EPS structural foam, rebar)
- Reusable materials may be effectively reused multiple times over a project’s duration (e.g., reusable formwork sets, deck shoring)
Figure 1 - Initial material type assignment
There are several strategies where using a combination of consumable vs. reusable materials can help a user achieve certain goals with their schedule. The following scenarios outline how consumable and reusable resources behave in practice.
Example Scenario 1 - Concrete Column Formwork:
Say a project has the following material resources available to create a concrete column as shown in Figure 2 below. Note that column formwork is defined as reusable, but basic formwork is classified as consumable. How do we determine whether a material should be defined as consumable or reusable?
Figure 2 - Project material parameters
Consumable Resource Behavior:
From Figure 1, we see that the project only has two (2) sets of column formwork available. Pretend for a moment that the column formwork has been classified as a consumable resource. Figure 3 shows a basic 3-task recipe where specific material actions have been assigned to each task using column formwork: requires for ‘form’ and supplies for ‘strip form.’ Actions define how the task treats the assigned material resource as shown in Figure 4.
Observe how the red line behaves; representing how the material is tracked throughout the activity.
Figure 3 - Formwork material behavior as a consumable resource. Note the resource quantity on the y-axis refers to the available quantity defined in the resource pool.
Figure 4 - Define the material’s action
Reusable Resource Behavior:
Figure 5 shows how the formwork material behaves when defined as reusable; all other material and task parameters remain unchanged. No matter the action, whether required or supplied, the reusable material is only in use for the duration of the task it is assigned to.
Figure 5 - Material behavior as a reusable resource. Note the resource quantity on the y-axis refers to the available quantity defined in the resource pool.
Which is better? Consumable or Reusable?
It depends. What do you wish to accomplish with your materials?
Scenarios aligned with defining materials as consumable:
- Tracking cumulative material costs over the project’s duration
- Every time a consumable material is used in ALICE, its cost is tallied
- Materials that are only used once
Defining materials as reusable is useful when:
- Constraining a quantity of a consumable material that can be placed over time (e.g., concrete)
- Tracking the usage frequency of material resources that are able to be reused multiple times on a project
Example Scenario 2 - Tracking Concrete Placement:
Suppose a project is in a dense urban area where traffic management is a critical constraint impacting site logistics. The project manager has reached an agreement with the local transit authority to cap the maximum daily number of concrete trucks that can queue by the project site to no more than 44 trucks per day. If we assume each truck carries approximately 10 CY of concrete, this limits us to placing 440 CY of concrete per day.
Figure 6 - We want to avoid this queue!
We must tell ALICE to constrain all concrete activities to comply with this set daily maximum through a combination of consumable and reusable materials.
- Concrete is typically designated as a consumable material resource in ALICE
- Quantity is often set as infinite since concrete procurement needs are driven by the project’s design
- ALICE tracks both the cumulative concrete material consumption and cost over the project’s duration
Figure 7 - Concrete material parameters
Recipes requiring concrete materials typically derive the concrete quantities parametrically from the CIM elements and are quantified by the model’s intrinsic units (i.e., cubic feet or cubic meters).
Figure 8 - Assigning material quantity via CIM parameter (i.e. el.volume)
Steps to Constrain Material Quantity:
1. Create a new reusable placeholder material resource called “Concrete_DailyMax”
- Quantity is defined as 11,880 cubic feet; which is the daily maximum of 440 CY converted to cubic feet
- The defined quantity for this material tells ALICE that all of the operations using this reusable material concurrently will never expend more than 11,880 cubic feet
- Remember: the CIM has intrinsic units, thus we must be mindful of how we convert quantities in ALICE
- Cost should be set to zero because this material is only a placeholder driving the maximum quantity and should not be used to calculate any costs as it is not material that will be used to build the project.
Figure 9 - Concrete_DailyMax is created as a placeholder to define a maximum concrete placement amount
2. Assign to every task using the concrete material both the concrete material and the ‘Concrete_DailyMax’ with both requiring equal quantities.
Figure 10 - Material resource tab for typical operation using concrete material and placeholder to cap maximum placement quantities
What’s Happening When Tracking Material This Placement?
1. Concrete, as a consumable resource with a cost, is being tracked cumulatively throughout the project’s duration
- ALICE will ‘place’ as much concrete as needed since the material quantity available is infinite, and the project’s needs are finite
- We can track the cost of concrete application over the project’s duration either daily, weekly, monthly, or totally.
2. Concurrently, when the reusable placeholder ‘Concrete_DailyMax’ material is assigned to every concrete task alongside the “real” consumable concrete material, we’re telling ALICE it’s not possible to “borrow” more than 11,880 cubic feet of concrete from the resource pool at one time.
- The placeholder reusable ‘Concrete_DailyMax’ establishes a rule for ALICE to follow when running simulations…
- ALICE is designed to schedule as many concurrent concrete activities as possible; yet with this rule applied, ALICE will never schedule a sequence of concurrent concrete activities that cumulatively use more than 11,880 cubic feet of concrete at the same time…
- If the combined quantity demand of the concurrently scheduled concrete activities reaches the cap of 11,880 cubic feet, ALICE knows only to proceed with scheduling successor activities when one of those concrete tasks completes, and ALICE reads that some reusable ‘Concrete_DailyMax’ material is replenished back to the resource pool.
Summary of Consumable vs. Reusable Behavior:
If we told ALICE we could only place a maximum of two (2) cubic feet of concrete at any given time for whatever reason, and we modeled our resource constraints similar to Example Scenario 2 above, ALICE would sequence our project as shown in Figure 11:
Figure 11 - Comparison between consumable and reusable concrete material quantification through a series of recipe operations
Understanding the behavior of consumable versus reusable materials in ALICE can unlock a user’s creative potential for modeling unique project constraints in ALICE. The principles outlined above can also be applied to constraining or tracking the application of labor and equipment resources as well. Don’t be afraid to test things out and push ALICE to the limit!